Some key dates in the robocalls controversy

March 26, 2011: Campaigning begins for the May 2 federal election. During the campaign, the commissioner of Canada elections gets about 100 complaints about nuisance phone calls or calls offering incorrect polling locations.

May 2, 2011: Hundreds of calls purporting to be from Elections Canada and giving erroneous poll information are made in the riding of Guelph. Investigators link the calls to pay-as-you-go cell phone belonging to a non-existent subscriber, Pierre Poutine.

Feb. 23, 2012: The first news reports about the robocalls investigation are published.

March 23, 2012: People from seven ridings go to Federal Court seeking to overturn the election results over the robocall issue. The case in one riding is dropped, six proceed.

March 29, 2012: The Chief Electoral Officer appeared at a Commons committee and reports that the number of complaints alleging specific occurrences of improper or fraudulent calls was near 800.

April 2, 2013: Former Conservative staffer Michael Sona is charged with having wilfully prevented or endeavoured to prevent an elector from voting.

May 23, 2013: A Federal Court judge finds fraud was a factor in the robocalls, and cites the Conservative voter database known as the Constituency Information Management System, or CIMS, as the source of the contact information used, but says it is not enough to overturn the election results.

April 24: The commissioner of Canada elections reports his office received 40,000 communications from Canadians about robocalls, although 96 per cent expressed concerns about robocalls without making any specific references to such calls. The report says the number of calls spiked dramatically as more media stories on robocalls appeared.